Acceleration of H ions for the Cyclotron Institute Upgrade ... posters/olvera_poster.pdf ·...
1
Abstract Acceleration of H - ions for the Cyclotron Institute Upgrade Project Juan A. Olvera Angelo State University REU 2010 Cyclotron Institute, Texas A&M University Advisor: Dr. Henry Clark The Cyclotron Institute at Texas A&M University is undergoing an upgrade that will allow for the production of radioactive ions for nuclear physics experiments. These ions will be produced with one of two ion guides, then collected, charge boosted and reaccelerated in the K500 cyclotron. The first radioactive ion beam for the project will be 27Si (T1/2=4.16s) at 15 MeV/u and will be produced through the reaction 27Al(p,n)27Si with 30 MeV protons. The recently recommissioned K150 cyclotron will accelerate the proton beams to intensity as high as 20 μA in order to produce sufficient amounts of radioactive ions. Rather than using an electrostatic deflector to extract the proton beam from the cyclotron, H - ions will be introduced into the cyclotron, accelerated to 30 MeV and then stripped to protons with a thin carbon foil at extraction. First tests show the extraction efficiency to be nearly 100% and that the technique greatly reduces interior activation of the cyclotron and problems from secondary radiation. The H - ion source, injection scheme and results from first tests will be presented. Overview and RIA The K150 Cyclotron will be used to accelerate H - ions and for the production of H + ions (protons) at extraction. This is part of a new concept called Rare Isotope Accelerator (RIA) which is a new approach at conducting nuclear physics experiments. The first proposed experiment that will be performed is shown in figure 1; figure 2 shows the layout of the beam lines and several components of interest. The arrows indicate the travel direction of the beam. Solutions to Extraction Problem H - Ion Production, Proton Production and Extraction, and First Results Other Upgrades to the K150 Cyclotron Future Work Acknowledgments Clark, Henry. “Project Management Plan for the Cyclotron Institute Upgrade at Texas A&M University” Kalvas, T. and Tarvainen, O. “Extending the Lifetime of Texas A&M H- Ion Source,” University of Jyvaskyla. 13 July 2010. Kalvas, T. et al., “Texas A&M H- Ion Source Extraction Design,” University of Jyvaskyla. 15 May 2009. Kim, G.J., “Status of the K150 Cyclotron Injection LIne,” 25 February 2010. Tabacaru, G., “Evaluation of the Radiation Shielding System of the 88” Cyclotron Vault at Texas A&M University.” Zhuravlev, B.V. et al;, “Analysis of neutron spectra in interaction of 22-MeV protons with nuclei,” Yadernaia Physics. Fig. 39(1984) 264-271 “Technical Review V,” January 22-23, 2009. References National Science Foundation (NSF) Dr. Henry Clark Department of Energy (DOE) Joe Brinkley Texas A&M University (TAMU) All the wonderful people at the Cyclotron Institute TAMU Cyclotron Institute Figure 1 Figure 2 Original Plan for Proton Production and Extraction Problems The K150 original plan called for the use of Electron Cyclotron Resonance (ECR2) source. The ECR2 source removes electrons, produces H + ions (protons) before injection into the cyclotron; these ions are then injected into the cyclotron, accelerated and extracted via a deflector. Figure 3 shows the injection diagram. ECR2 90 deg magnet Figure 3 However, problems were observed with the extraction system of the original plan. Among these problems were activation of the deflector causing secondary radiation, loss of run time, and about 50% loss of beam at best. Figure 3 shows the injection line. Figure 4 shows a cross-section of the vault area and the radiation distribution due to this activation, mostly neutrons and gamma rays. Figure 5 shows gamma ray activity and dose rates after irradiation of deflector for 10 days. Distance: .5 meters Rad worker limit: 5000mRem/year 4.5 0.1 Na-22 gamma source 11865.8 265.811 5 days 17421.7 390.27 3 days 30632.7 686.216 1 day 45918.9 1028.649 1 hour 52144.3 1168.108 10 min Dose Rate(mRem/hr) Activity(mCi) Time Distance: .5 meters Rad worker limit: 5000mRem/year 4.5 0.1 Na-22 gamma source 11865.8 265.811 5 days 17421.7 390.27 3 days 30632.7 686.216 1 day 45918.9 1028.649 1 hour 52144.3 1168.108 10 min Dose Rate(mRem/hr) Activity(mCi) Time Figure 4 Figure 5 Several solutions were available to solve this problem. We could build a special deflector for protons, but we would need one for each proton energy, ideally. The deflector needs to be biased at about 80KV, which causes sparking and degrades the surface which means it deflects less. We could also build one out of Aluminum, but it would still be very hot, complicating maintenance. The third, and best option, was to install an H - ion source. The advantages were 100% extraction efficiency, no need for deflector, no danger of high voltage, and production of high intensity protons and deuteron beams. Figure 6 shows the placement of the H - source, the current configuration is shown on the right. Source Source Spool & steering magnet Figure 6 H - ions are produced when a “hot” electron excites a Hydrogen molecule, the molecule then moves into a filter field where a “cold” electron attaches itself to one of the Hydrogen atoms creating a negatively charged ion, an H - ion. This is shown in figure 7, along with the reactions that create the ion. Figure 8 shows the multi-cusp magnetic field that contains the plasma toward the center of the volume. Figure 9 shows the “tilt” suggested for extraction of the beam from the source. Excited Molecules Dissociative Attachment Figure 7 Figure 8 Source “Tilt” suggested by Olli Tarvainen, JYFL Puller with e - Dump Magnets Plasma Electrode Einzel Lens H - ions e- Figure 9 The production of protons occurs when the H - ions collide with a carbon foil 2 microns thick near the exit of the cyclotron. Upon collision, the 2 electrons are stripped away by the foil and an H + (proton) emerges out the other side, this process is depicted in figure 10. Once the protons are produced, the change in charge causes the protons to be deflected out of the cyclotron as shown in figure 11. The highest current achieved from first results was 24.5μA at extraction for a brief moment with a steady current of 10μA at extraction and 60+ hours of filament usage without failure. Figure 10 Figure 11 Raised water cooling system – reduced clutter. (Picture 1) Installed door switches in HV cage – safety precaution. (Picture 2) Installed safety cage to isolate HV near source. (Picture 3) Installed spool, steering magnet, and platform. (Picture 4) Installed gas lines, air lines, electrode covers, wired some interlock lines. Picture 1 Picture 2 Picture 3 Picture 4 Test beam focusing, throughput down the beam line Joe Brinkley will develop program to optimize beam from source Improve ion source – filament is limiting factor Inductively coupled rf-discharge, eliminates filament Inductively heated thermionic emission cathode Extends the lifetime of the filament – further development needed
Transcript of Acceleration of H ions for the Cyclotron Institute Upgrade ... posters/olvera_poster.pdf ·...
Abstract
Acceleration of H- ions for the Cyclotron Institute Upgrade ProjectJuan A. Olvera
Angelo State UniversityREU 2010 Cyclotron Institute, Texas A&M University
Advisor: Dr. Henry Clark
The Cyclotron Institute at Texas A&M University is undergoing an upgrade that will allow for theproduction of radioactive ions for nuclear physics experiments. These ions will be produced with one oftwo ion guides, then collected, charge boosted and reaccelerated in the K500 cyclotron. The firstradioactive ion beam for the project will be 27Si (T1/2=4.16s) at 15 MeV/u and will be produced throughthe reaction 27Al(p,n)27Si with 30 MeV protons. The recently recommissioned K150 cyclotron willaccelerate the proton beams to intensity as high as 20 µA in order to produce sufficient amounts ofradioactive ions. Rather than using an electrostatic deflector to extract the proton beam from thecyclotron, H- ions will be introduced into the cyclotron, accelerated to 30 MeV and then stripped toprotons with a thin carbon foil at extraction. First tests show the extraction efficiency to be nearly 100%and that the technique greatly reduces interior activation of the cyclotron and problems from secondaryradiation. The H- ion source, injection scheme and results from first tests will be presented.
Overview and RIAThe K150 Cyclotron will be used to accelerate H- ions and for the production of H+ ions (protons) atextraction. This is part of a new concept called Rare Isotope Accelerator (RIA) which is a new approachat conducting nuclear physics experiments. The first proposed experiment that will be performed isshown in figure 1; figure 2 shows the layout of the beam lines and several components of interest. Thearrows indicate the travel direction of the beam.
Solutions to Extraction Problem
H- Ion Production, Proton Production and Extraction, and First Results
Other Upgrades to the K150 Cyclotron
Future Work
Acknowledgments
Clark, Henry. “Project Management Plan for the Cyclotron Institute Upgrade at Texas A&M University”Kalvas, T. and Tarvainen, O. “Extending the Lifetime of Texas A&M H- Ion Source,” University of Jyvaskyla. 13 July 2010.Kalvas, T. et al., “Texas A&M H- Ion Source Extraction Design,”
University of Jyvaskyla. 15 May 2009.Kim, G.J., “Status of the K150 Cyclotron Injection LIne,” 25 February 2010.Tabacaru, G., “Evaluation of the Radiation Shielding System of the 88” Cyclotron Vault at Texas A&M University.”Zhuravlev, B.V. et al;, “Analysis of neutron spectra in interaction of 22-MeV protons with nuclei,” Yadernaia Physics. Fig. 39(1984) 264-271“Technical Review V,” January 22-23, 2009.
References
National Science Foundation (NSF) Dr. Henry ClarkDepartment of Energy (DOE) Joe BrinkleyTexas A&M University (TAMU) All the wonderful people at the Cyclotron InstituteTAMU Cyclotron Institute
Figure 1
Figure 2
Original Plan for Proton Production and Extraction ProblemsThe K150 original plan called for the use of Electron Cyclotron Resonance (ECR2) source. The ECR2source removes electrons, produces H+ ions (protons) before injection into the cyclotron; these ions arethen injected into the cyclotron, accelerated and extracted via a deflector. Figure 3 shows the injectiondiagram.
ECR2
90 deg magnet
Figure 3
However, problems were observed with the extraction system ofthe original plan. Among these problems were activation of thedeflector causing secondary radiation, loss of run time, andabout 50% loss of beam at best. Figure 3 shows the injectionline. Figure 4 shows a cross-section of the vault area and theradiation distribution due to this activation, mostly neutrons andgamma rays. Figure 5 shows gamma ray activity and dose ratesafter irradiation of deflector for 10 days.
Distance: .5 meters
Rad worker limit: 5000mRem/year
4.50.1Na-22 gamma source
11865.8265.8115 days
17421.7390.273 days
30632.7686.2161 day
45918.91028.6491 hour
52144.31168.10810 min
Dose Rate(mRem/hr)Activity(mCi)Time
Distance: .5 meters
Rad worker limit: 5000mRem/year
4.50.1Na-22 gamma source
11865.8265.8115 days
17421.7390.273 days
30632.7686.2161 day
45918.91028.6491 hour
52144.31168.10810 min
Dose Rate(mRem/hr)Activity(mCi)Time
Figure 4Figure 5
Several solutions were available to solve this problem. We could build a special deflectorfor protons, but we would need one for each proton energy, ideally. The deflector needs tobe biased at about 80KV, which causes sparking and degrades the surface which means itdeflects less. We could also build one out of Aluminum, but it would still be very hot,complicating maintenance. The third, and best option, was to install an H- ion source. Theadvantages were 100% extraction efficiency, no need for deflector, no danger of highvoltage, and production of high intensity protons and deuteron beams. Figure 6 shows theplacement of the H- source, the current configuration is shown on the right.
Source
SourceSpool & steering magnet
Figure 6
H- ions are produced when a “hot” electron excites a Hydrogen molecule, the moleculethen moves into a filter field where a “cold” electron attaches itself to one of the Hydrogenatoms creating a negatively charged ion, an H- ion. This is shown in figure 7, along with thereactions that create the ion. Figure 8 shows the multi-cusp magnetic field that contains theplasma toward the center of the volume. Figure 9 shows the “tilt” suggested for extractionof the beam from the source.
Excited Molecules
Dissociative Attachment
Figure 7
Figure 8
Source “Tilt” suggested by Olli Tarvainen, JYFL
Puller with e- Dump Magnets
Plasma Electrode
Einzel Lens
H-
ions
e-
Figure 9
The production of protons occurs when the H- ions collide with a carbon foil 2 microns thick nearthe exit of the cyclotron. Upon collision, the 2 electrons are stripped away by the foil and an H+
(proton) emerges out the other side, this process is depicted in figure 10. Once the protons areproduced, the change in charge causes the protons to be deflected out of the cyclotron asshown in figure 11. The highest current achieved from first results was 24.5µA at extraction for abrief moment with a steady current of 10µA at extraction and 60+ hours of filament usage withoutfailure.
Figure 10
Figure 11
Raised water cooling system – reduced clutter. (Picture 1)Installed door switches in HV cage – safety precaution. (Picture 2)Installed safety cage to isolate HV near source. (Picture 3)Installed spool, steering magnet, and platform. (Picture 4)Installed gas lines, air lines, electrode covers, wired some interlock lines.
Picture 1 Picture 2 Picture 3
Picture 4
Test beam focusing, throughput down the beam lineJoe Brinkley will develop program to optimize beam from source Improve ion source – filament is limiting factor
Inductively coupled rf-discharge, eliminates filamentInductively heated thermionic emission cathode
Extends the lifetime of the filament – further development needed
